Network security smart load balancing

ABSTRACT

A system and method for protecting data communications in a system including a toad-balancer connected to a cluster of security network components, e.g. firewall node. The load-balancer transfers one or more of the data streams respectively to the security components. The security network components transmit control information to the load-balancer and the control information includes an instruction regarding balancing load of the data streams between said components; The load-balancer balances load based on the control information. Preferably, network address translation (NAT) is performed by the load-balancer based on the control information or NAT is performed by the security network component and the control information includes information regarding an expected connection based on NAT. Preferably, when the data communications includes an encrypted session, an encrypted connection of the encrypted session is identified based on the control information and the balancing of the load maintains stickiness of said encrypted connection.

This is a Continuation of U.S. patent application Ser. No. 11/345,341, filed Feb. 2, 2006

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to security of data networks and specifically to a system and method for providing a high-speed firewall which protects internal networks while processing complex connections.

Firewall techniques involve using a set of rules to compare incoming data packets to a defined security policy. A firewall accepts and denies traffic between two or more network domains. In many cases, there are three domains where the first domain is an internal network such as in a corporate organization. Outside the internal network is a second network domain where both the internal network and the outside world have access, sometimes known as a “demilitarized zone” or DMZ. The third domain is the external network of the outside world.

A firewall regulates the flow of data packets. A packet includes a header and a payload. The header includes header information (i.e. header parameters), which typically includes a source and destination address, and source and destination port numbers, and a protocol. The payload includes data conveyed by the packet from its source to its intended destination. The firewall, which is situated between the source and destination, intercepts the packet. The firewall filters packets based upon header information and a rule previously loaded into the firewall. The rule correlates a pattern in the header of a packet with a prescribed action, either PASS or DROP or other actions like encrypt, perform network address translation (NAT) send a RESET packet, generate logs, and perform content inspection. The filter identifies the rule that applies to the packet based upon the packet's header, and then implements the rule's prescribed action. When a DROP action is performed, the packet is blocked (deleted), and does not reach its intended destination. When a PASS action is performed, the packet is passed on toward its intended destination. The set of rules loaded into a firewall reflect a security policy, which prescribes what type of information is permissible to pass through the firewall, e.g., from which source, to which destination, and for which application.

To ensure sufficient capacity of a firewall, it is common to construct clusters which include typically a number of firewall nodes sharing a common network address, and connections are typically directed to the cluster by means of a cluster network address. Additionally, the nodes typically have node-specific addresses, e.g. MAC addresses. In a cluster, if the firewall nodes have a common cluster network address, all the firewall nodes read all data packets arriving at the cluster. Consequently, there has to be an arrangement for distinguishing which data packets belong to which node. Each node should process only those packets that are assigned to it and not receive or receive but ignore other data packets.

Connections directed to a cluster of network elements are directed to different nodes of the cluster on the basis of predefined distribution criteria. Frequently, distributing is done so that each firewall node filters all arriving data packets and decides on the basis of the header field(s) of the packet whether that particular node needs to process that particular packet. Frequently, specific sets of hash values are allocated to the nodes and a hash value for a data packet is calculated using a predetermined hash function and certain header fields of the data packet. Typically the header fields that are used for calculating hash values for TCP/IP (Transfer Control Protocol/Internet Protocol) or for UDP/IP (User Datagram Protocol/Internet Protocol) are source address, source port, destination address and destination port. When a data packet directed to the cluster network address arrives at the cluster, a hash value is calculated on the basis of some header fields of the data packet, and the resulting hash value defines which node processes the data packet. Typically, all nodes filter all arriving data packets by calculating hash values for them, and then decide on the basis of the hash values regarding which packets which belong to each node. Methods other than calculating a hash from the header connection information may be used for distributing the data packets.

Several prior art techniques are used to determine distribution of packets among the firewall nodes. Often, a return to sender (RTS) technique is used in which for each connection the load balancer learns the MAC address of the firewall node so that replies from servers are directed to the correct firewall. Sometimes the load between the firewall nodes is balanced statically without any dynamic adjustment of load between the firewall nodes and/or a new connection is assigned according to a “round robin” technique distributing each new connection to the next firewall node in a queue without regard to the actual availability of the node. A simple query, such as a “ping” may be used and the time to respond to the “ping” is measured to roughly assess the availability of the firewall node.

According to U.S. Pat. No. 6,880,089, a firewall clustering system connects two or more firewalls between an internal network and an external network. Firewalls maintain client-server state information. Flow controllers are connected to the firewalls and placed on both the internal “trusted” side and the external “untrusted” side of the firewalls. Flow controllers are placed on both sides of the firewalls to ensure that traffic for a given client-server connection flows through the same firewall in both inbound and outbound directions. The firewalls perform filtering operations and/or network address translation (NAT) services.

According to a method disclosed in US patent application publication 20030002494, node-specific lists of connections are maintained which specify for which connections each node of a firewall is responsible. A data packet, which initiates opening of a new connection, is processed in a node determined by a distribution decision according to predetermined distribution criteria. The first data packets are thus distributed to the cluster nodes. A data packet, which relates to an opened packet data connection, is processed in that node in whose connection list the opened packet data connection is specified. Changing the distribution criteria is required when load is not in balance between the nodes, or when a new node is added or removed to/from the cluster.

The prior art addresses load balancing between firewall nodes for “simple connections”. An important requirement from a load balancing device is to maintain connection stickiness, so that all packets belonging to the same connection will be forwarded to same firewall. Standard load balancers available on the market today can provide connection stickiness for simple connection types. However, for complex connections, such as when control and data are on different connections, e.g. FTP or voice over IP connections when NAT is applied, the NAT information is inserted into the payload, the prior art method load balancing systems and methods are not appropriate, and different firewalls may be processing different packets of the same complex connection.

There is thus a need for, and it would be highly advantageous to have a system and method in which one or more firewalls of a firewall cluster manages the load balancer specifically by inspecting the content, i.e. payload, of packets of a complex connection, and directs a switch regarding expected connections related to the complex connection.

SUMMARY OF THE INVENTION

The term “blade and the term “node” are used herein interchangeably. The terms “firewall” and “firewall node” are used herein interchangeably. The firewall is a computer running firewall software, hardware and/or firmware. An example of firewall software is Check Point Firewall-1/VPN-1. (Check Point Software

Technologies Ltd., 3A Jabotinsky St., Ramat Gan, ISRAEL). The term “firewall cluster” is used to denote a cluster of firewalls. The term “security network component” as used herein is a network component, such as a firewall or server, which performs a security function such as inspection, NAT, and encryption. The term “switch” denotes a load balancing switching device. The term “switch” and the term “load balancer” are used herein interchangeably. The term “firewall identifier” is a unique number identifying the specific firewall. A firewall is identified by the physical port number it is connected to and/or a MAC address. The firewall identifier may be related to or corresponding to, such as with a look up table, to MAC address, or switch port number. The term “stickiness” or “persistence” as used herein is used to denote the property that all packets of the same session or related connections are processed by the same security network component. The terms “complex connection” and “session” are used herein interchangeably.

According to the present invention there is provided a method for protecting data communications in a system including a load-balancer connected to a cluster of security network components, e.g. firewall node. The load-balancer transfers one or more of the data streams respectively to the security components. The security network components transmit control information to the load-balancer and the control information includes an instruction regarding balancing load of the data streams between said security network components; The load-balancer balances load based on the control information. Preferably, network address translation is performed by the load-balancer based on the control information or network address translation is performed by the security network component and the control information includes information regarding an expected connection based on the network address translation. Preferably, when the data communications includes an encrypted session, an encrypted connection of the encrypted session is identified based on the control information and the balancing of the load maintains stickiness of said encrypted connection. Preferably, the control information specifies one of the security network components to receive a new connection. Preferably, a packet is received by the security network component of the cluster through the load-balancer, and the packet is of a connection of a communications session; the security network component reads at least one datum from the packet and the control information is based on the datum and specifies an expected connection. Preferably, the datum is in a payload of the packet. Preferably, encryption is performed by the security network component, and the control information includes information regarding an expected connection based on the encryption. Preferably, the communications session is encrypted by the security network component and the load-balancer identifies one or more of the data streams of the encrypted communications session based on the control information. Preferably, the expected connection includes an expected packet of the session. Preferably, upon receiving an expected packet of the expected connection, the expected packet is forwarded based on the control information and preferably, from the load balancer to selectively either the security network component or to a network connected to the load balancer and bypassing said security network component. Preferably, the control information specifies an expected client-to-server connection and an expected server-to-client connection, and a condition is fulfilled: (i) a parameter of the client-to-server connection differs from a destination parameter of the server-to-client connection; and or (ii) a destination parameter of the client-to-server connection differs from a source parameter of the server-to-client connection. Preferably, the packet is of a multicast connection and the control information directs the load-balancer to direct all multicast packets of the multicast connection to one of the network components. Preferably, when the load-balancer reaches a maximum capacity, one or more connections are dropped and the network component is informed of the dropped connections.

According to the present invention there is provided a system for protecting data communications. The system includes a cluster of network components, and a load-balancer which connects the network components. Data streams are transferred respectively to the security network components and a load balancer receives a command from one or more security network components, the command including an instruction regarding balancing load of the data streams between the security network components. Preferably, network address translation is performed by either one of the security network components or the load-balancer. Preferably, the command includes control information based on at least one datum received by one or more of the security network component. Preferably, the command specifies an expected connection, and the expected connection includes an expected packet. Preferably, the security network components is an independent gateway connected through a network interface, a blade connected to the load balancer and/or two or more of the security components are implemented using independent processors on the same circuit board.

According to the present invention there is provided a system for protecting data communications. The data communications includes sessions wherein connection information is included as arguments of control commands of the sessions. The system includes a cluster of network components; and a switch which connects the network components to at least one network; and a protocol which configures the network components and the switch so that the network components read the connection information; and commands from the network components to the switch allow maintaining connection stickiness in the sessions, when connection stickiness guarantees that all packets of each of the sessions are processed by a single network component. Preferably, the protocol includes a new-connection command, wherein the network component reads the connection information and based on the connection information, transfers expected connection information to the switch. Preferably, the protocol includes a register multicast command wherein all packets of related multicast connections are processed by a single network component.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:

FIG. 1 is a drawing of a cluster of firewall nodes at a gateway between two networks, a system which is used for the method of the present invention

FIG. 2 is a prior art flow drawing of the prior art for processing simple connections;

FIG. 3 is a flow drawing of the present invention for processing complex connections; and

FIG. 4 is a drawing illustrating commands used in an example of a protocol of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is of a system and method for smart load balancing of a cluster of firewall nodes. Typically it is advantageous that in a cluster of firewall nodes, a single firewall node processes all the packets of a connection. For simple connections, it is typically sufficient to read header information of packets to insure that the same firewall node handles all the packets of the simple connection. However, for complex connections or sessions, often control information specifying upcoming connections is transferred as arguments of control commands, i.e., in the payloads of the packets of the control command. The present invention utilizes the control information to maintain connection stickiness by transferring information using a special protocol to a switch connecting the firewall nodes. The switch subsequently transfers new connections to the appropriate firewall node.

The principles and operation of a system and method of smart load balancing (SLB), according to the present invention, may be better understood with reference to the drawings and the accompanying description.

It should be noted, that although the discussion herein relates to load balancing between firewall nodes in a cluster, the present invention may, by non-limiting example, alternatively be configured as well using load balancing in a cluster of other network components such as in a cluster of servers. A difference between load balancing in a firewall cluster and load balancing in a gateway with a cluster of servers is that the server is typically identified by a unique IP address while in firewall nodes a connection, e.g. packet, does not include an identifier specifying which firewall node will handle the connection.

Before explaining embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of design and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

By way of introduction, principal intentions of the present invention are to: provide high speed (˜10 Gbs) load balancing through a cluster of firewall nodes and maintain: “stickiness”, i.e. to process all packets of the same connection using the same firewall node, even for control and data packets of the same complex connection.

Referring now to the drawings, FIG. 1 illustrates a system 10 used according to an embodiment of the present invention. System 10 or SLB device 10 is a symmetric configuration of two switches 11 which switch data traffic at a gateway between an internal network 17 and an external network 15. Switches 11 are configured to decide which firewall node 13 is used of firewall cluster 19 to process data and control packets traveling between internal network 17 and external network 15. Alternatively, in a different configuration a single switch 11 may be used with firewall cluster 19. Both switches 11 and firewall nodes 13 are computers or computing machines each including a processor and memory and appropriate interfaces (not shown). Different embodiments of the present invention include a number of hardware configurations including multiple processors on a single circuit board, or alternatively multiple boards (or blades) each including a single processor or alternatively different nodes connected via a network. A basic requirement from switch 11 is to perform load-balancing between the firewalls 13 with stickiness. Switch 11 may employ known algorithms for load balancing e.g. Round-Robin, Server-Load, Hash.

In another embodiment of the present invention a single switch 11 is connected respectively through different ports to external network, e.g. Internet, 15 and to LAN 17. Firewall 13 needs to send control commands to switch 11 including a description of the connections both on the Internet side and on the LAN side.

Reference is now made also to FIG. 2 which shows a prior art method for balancing load of simple connections through system 10. A packet of a simple connection arrives (step 20) at switch 11. Typically, switch 11 reads (step 22) the header of the packet and checks to determine if the received packet is of an existing connection or a new connection (decision block 24). If the received packet is a first packet of a new connection then switch 11 decides (step 26) to which firewall node 13 to send the received packet based on a previously defined rule stored in memory. Otherwise, if the received packet is not a first packet but a packet of an existing connection, then switch 11 look up (step 28) the connection and switches (step 30) the packet to the correct firewall node 13, typically with the same firewall node 13 processing all the packets of the same connection.

Reference is now made to FIG. 3, a flow diagram of a processing method for complex connections or sessions, according to an embodiment of the present invention. In the example of FIG. 3, a control connection of a complex connection is established in the same manner as a simple connection. The example of FIG. 3 uses an FTP port command, however the present invention is applicable to any complex connection which include control and data connections in which information regarding the data connection is included in an argument of the control connection. The present invention is further applicable to a session involving multiple control connections which are related to each other. An FTP PORT command reaches (step 31) switch 11. An FTP port command is a control command which includes as an argument of the command a client port to be used in a passive data connection associated with the FTP port command In the example of FIG. 3, the port command 1.1.1.1 PORT 123 comes from a client of IP address 1.1.1.1 and requests data using client port 123. The port command is passed (step 33) by switch 11 to a firewall node 13, e.g. #4. Firewall node 13 reads (step 35) the port command, included in the payload(s) of the packet(s). Based on the information read in the payload of the packet(s) carrying the PORT command, firewall node 13 transmits (step 37) a control command to switch 11 to expect connections as defined from the arguments of the PORT command In the example of FIG. 3, network address translation is being used so two connections are expected related to the FTP connection, where C denotes client and S denotes server. The expected connections are typically specified by source IP address/source port and protocol, e.g. TCP. Because of network address translation, the IP address of client C is 1.1.1.1 and the translated IP address C′ is different e.g. 4.4.4.4. Similarly, the public IP address of server S is 2.2.2.2 and the translated address S′ is 3.3.3.3. Firewall 13 typically transmits along with the control command for the expected connections a firewall node, e.g. #4 to handle the connections as well as a timeout parameter, e.g. 60 which causes the connection to expire 60 seconds after last packet is received, as follows:

C→S: 1.1.1.1/123 2.2.2.2/124 TCP S′ C′: 3.3.3.3/1001 4.4.4.4/1002 TCP Handled by: Firewall node #4, Timeout: 60

When an expected data connection is opened, switch 11 already expects the data connection, switch 11 performs the necessary network address translation and forwards the packets to the correct cluster member, e.g. firewall node 13. Subsequent packets of the same session are matched to one of the keys of this connection and therefore directed to the same cluster member, firewall node 13 #4. In an alternative embodiment, firewall nodes 13 perform the network address translation (NAT) and in this case commands sent from firewall node 13 to switch 11 do not necessarily include NAT information.

In other embodiments of the present invention, one or more additional switches between firewall cluster 19 and the server may receive commands from firewall nodes 13. Optionally, there may be more than one firewall clusters 19 physically separated and cooperating with each other using multiple switches 11.

In certain protocols, especially voice over IP protocols, a session includes both control and data connections. Firewall node 13 typically opens a data connection and based on data found, e.g. in a payload of a packet of a control connection, firewall node 13 performs a specific action.

According to an embodiment of the present invention, smart load balancing of firewall nodes 13 may be generalized to include other network components 13 such as a cluster of servers 13. Servers 13 that are balanced may also be configured to decide which future simple connections should be directed to each server 13 as part of a complex connection or session. The decision of each server 13 is sent back to a switch 11 connecting servers 13 using a special protocol, even the same protocol as is used for smart load balancing of firewall nodes 13. The decision at the server can be performed in an application running on the server if the application has access to information regarding future connections. An alternative system, according to an embodiment of the present invention includes in server 13 a packet inspecting module which reads contents of the packets, decides which future connections will be sent to the server 13 and communicates the decision to switch 11.

According to other embodiments the present invention supports static and dynamic encryption protocols, e.g. VPN. In the static case, a centralized management installs information about encryption domains in security components 13 and security components 13 communicate information to load-balancer 11 regarding the partition of encrypted connections between security components 13. In the dynamic case, a routing protocol is used between security components 13 (and also with other external routers or VPN gateways) to decide which component 13 will handle which encrypted connections. Once the decision is made, and information regarding the partition of encrypted connections is known, security network components 13 transmit control information regarding the balancing of load to load-balancer 11.

Another option is that the load-balancer 11 allows one security network component 13 to establish a tunnel (e.g. Phase1 and Phase2 of IPSEC VPN) and once a tunnel is established load-balancer 11 receives an instruction from security network component 13 how to identify packets that relate to to that tunnel Afterwards, all packets from the same VPN tunnel are directed to the same security network component 13, (e.g. using Security Parameters Index, SPI, that appears in the AH header of IPSEC packet.)

Smart Loading Balancing Protocol

Reference is now made to FIG. 4 illustrating an example of a smart load balancing protocol which allows firewall nodes 13 to implement the process 30 and to override the default decision made by switch 11. Switch 11 receives commands from the firewalls 13: Typically, all firewalls 13 have the same priority, all commands are asynchronous, some commands may require switch 11 to send a reply, and the protocol is UDP based.

Commands Description

-   41 Register Firewall: -   A register firewall command 41 initializes the connection between a     firewall 13 and switch 11. When firewall 13 goes online, switch 11     is notified so load balancing may begin. A parameter of the register     firewall command 41 is the firewall identifier. -   Switch 11 replies with an acknowledgment 42, e.g. ACK. After     receiving the register firewall command 41, switch 11 will begin     forwarding traffic to firewall 13 according to the current load     balancing algorithm.

43 Deregister Firewall:

-   The deregister firewall command 43 directs the SLB device 10 to     ignore a firewall 13. Some of firewall nodes 13 may need to go     off-line for maintenance. Additionally, an administrator may choose     to use some of the machines for other purposes. A parameter of the     deregister firewall command 43 is the firewall identifier. After     firewall 13 sends a deregister firewall command to switch 11,     existing connections will be forwarded to firewall 13 but new     connections will be directed to other firewalls 13. If a firewall 13     stops responding i.e. crashes, switch 13 is expected to forward     existing connections from firewall 13 to other firewalls 13. -   45 New Connection: -   The new connection command 45 instructs switch 11 to direct a     connection to a specific firewall 13. In order to maintain     stickiness for complex connections, a firewall 13 can send a new     connection command to switch 11. Since network address translation     (NAT) typically performed by switch 11 may cause both directions to     look different, the command contains two expected connections switch     11 should handle. -   The new connection command typically includes up to four parameters     as follows: -   1. Client to Server connection: Source IP, Source Port, Destination     IP, Destination Port, Protocol -   2. Server to Client connection: Source IP, Source Port, Destination     IP, Destination Port, Protocol -   3. Expiration time in seconds -   4. Firewall Identifier -   Switch 11 may reply with a new connection reply 46 with a connection     identifier and a firewall identifier. -   After receiving the New-connection command, switch 11 directs     packets that belong to this connection to firewall node 13     corresponding to the firewall identifier (parameter 4), start the     expiration timer (e.g. each packet resets this timer), and if such a     connection is already assigned to a firewall 13, switch 11 notifies     the requesting firewall 13 about which firewall 13 is the current     handler.

47 Delete Connection:

-   The Delete-connection command 47 is sent by a firewall when a     connection is terminated. A parameter of the Delete-connection     command is a connection identifier. Upon receiving such a command,     switch 11 should immediately stop forwarding packets of the     connection to relevant firewall 13. Packets from this connection, if     any, should be treated as a new connection by switch 11.

49 Query Connection

-   The Query-connection command 49 is sent by firewall 13 to get     information about a connection. A parameter is the connection     identifier. The switch replies with connection information as     follows: -   1. Client to Server connection: Source IP, Source Port, Destination     IP, Destination Port, Protocol -   2. Server to Client connection: Source IP, Source Port, Destination     IP, Destination Port, Protocol -   3. Expiration time in seconds -   4. Firewall Identifier

51 Register Multicast:

-   The register multicast command directs SLB device 10 to register a     multicast connection. The parameters include a firewall identifier,     multicast address and a port For some kinds of multicast     connections, e.g. Dynamic routing daemon, only one firewall 13 can     handle the connection A Register-Multicast command should direct a     multicast packet to a specific firewall 13.

53 New Template:

-   In some cases, many connections are opened between the same client     and server. -   In order to save many similar new-connection commands, a     New-Template command will be issued. -   Each connection that matches the template results in a new     connection similar to a connection created by a new-connection     command. Parameters of the new template command include: -   1. Firewall Identifier -   2. Client to Server connection: Source IP, Destination IP,     Destination port, Protocol 3. Server to Client connection: Source     IP, Source port, Destination IP, Protocol -   4. Template Expiration time. -   5. Connection Expiration time (reset on each packet).

56 Connection Dropped

-   A connection dropped command is sent by switch 11 to firewall 13     when a connection is dropped because switch 11 is at maximum     capacity and can not handle the connection. A parameter of the     Connection-dropped command is the connection identifier. Since     switch 11 is the front end for SLB device 10, switch 11 is exposed     to denial-of-service attacks. -   When switch 11 is at maximum capacity, it should drop connections     according to some kind of throttling algorithm, such as LRU (least     recently used). In such scenarios, switch 11 is expected to notify     the specific firewall 13 about the dropped connections.

57 Heartbeat

A Heartbeat command is sent by firewall 13 to switch 11 so that switch 11 can identify cases when firewall 13 is down. A parameter of the Heartbeat command is the firewall identifier.

Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of the invention may be made. 

1. A method for protecting data communications, the method comprising the steps of: (a) providing at least one load-balancer operatively connecting a cluster of security network components, said at least one load-balancer transferring a plurality of sessions respectively to said security components; (b) transmitting control information from one of said security network components to said at least one load-balancer, wherein said control information includes an instruction, regarding balancing load of said sessions between said security network components, that identifies at least one second said session, that is related to a first said session that said at least one load-balancer is transferring to said one security network component, as a session that is to be transferred only to said one security network component; and (c) balancing load by said at least one load-balancer based on said control information.
 2. The method according to claim 1, further comprising the step of: (d) performing network address translation by said at least one load-balancer, wherein said network address translation is based on said control information.
 3. The method according to claim 1, further comprising the step of: (d) performing network address translation by said at least one security network component, wherein said control information includes information regarding said at least one second session based on said network address translation.
 4. The method according to claim 1, further comprising the step of: (d) performing encryption by said at least one security network component, wherein said control information includes information regarding said at least one second session based on said encryption.
 5. The method according to claim 1, wherein said first session is an encrypted session, the method further comprising the step of: (d) identifying said at least one second session as an encrypted session based on said control information.
 6. The method according to claim 1, wherein said control information specifies said one security network component to receive said at least one second session as a new session.
 7. The method, according to claim 1, further comprising the steps of (d) receiving at least one packet by said one security network component of said cluster through said at least one load-balancer, wherein said packet is of said first session; and (e) reading by said one security network component at least one datum from said packet; wherein said control information is based on said at least one datum and specifies said at least one second session.
 8. The method according to claim 7, wherein said at least one datum is in a payload of said packet.
 9. The method according to claim 7, further comprising the steps of: (f) upon receiving a packet of one of said at least one second session, forwarding said packet of said one second session based on said control information.
 10. The method, according to claim 9, wherein said forwarding is from said load balancer to selectively either said one security network component or to a network operatively connected to said load balancer thereby bypassing said one security network component.
 11. The method according to claim 1, wherein said control information specifies an expected client-to-server connection and an expected server-to-client connection, wherein at least one condition is fulfilled selected from the group of: (i) at least one source parameter of said client-to-server connection differs from at least one destination parameter of said server-to-client connection; and (ii) at least one destination parameter of said client-to-server connection differs from at least one source parameter of said server-to-client connection.
 12. The method according to claim 1, wherein said at least one second session is a multicast session and said control information directs said at least one load-balancer to direct all multicast packets of said multicast session to said one network component.
 13. The method according to claim 1, further comprising the steps of: upon said at least one load-balancer reaching a maximum capacity: (d) dropping at least one said session; and (e) informing said security network component of said dropping.
 14. A system for protecting data communications, the system comprising: (a) a cluster of security network components; and (b) at least one load balancer which operatively connects said security network components by transferring a plurality of sessions respectively to said security network components wherein said at least one load balancer receives a command from one of said security network components, wherein said command includes an instruction regarding balancing load of said sessions between said security network components, that identifies one second said session, that is related to a first said session that said at least one load-balancer is transferring to said one security network component, as a session that is to be transferred only to said one security network component.
 15. The system, according to claim 14, wherein network address translation is performed by a component selected from the group consisting of said security network components and said at least one load-balancer.
 16. The system, according to claim 14, wherein said command includes control information based on at least one datum received by said one security network component.
 17. The system, according to claim 14, wherein said command specifies said second session as a new session.
 18. The system, according to claim 14, wherein at least one of said security network components includes an independent gateway connected through a network interface.
 19. The system, according to claim 14, wherein at least one of the security network components is a blade connected to said at least one load balancer.
 20. The system, according to claim 14, wherein at least two of the security network components are implemented at least in part by independent processors on one circuit board.
 21. A system for protecting data communications, the data communications including sessions wherein connection information is included as arguments of control commands of the sessions, the system comprising: (a) a cluster of security network components; (b) at least one load balancer which operatively connects said security network components to at least one network; and (c) a protocol configuring said security network components and said at least one load balancer so that (i) said security network components read said connection information; and (ii) commands from the network components to said at least one load balancer allow maintaining connection stickiness in said sessions, wherein connection stickiness guarantees that all packets of said sessions that are related to each other are processed by a single said security network component.
 22. The system, according to claim 21, wherein said protocol includes a new-connection command, wherein one of said security network components reads said connection information from a packet of a first said session and based on said connection information, instructs said at least one load balancer to transfer, only to said one security network component, all packets of a second said session that is related to said first session.
 23. The system, according to claim 21, wherein said protocol includes a register multicast command wherein all packets of related multicast sessions are processed by a single said security network component. 